Piezoelectric body, piezoelectric device, and liquid discharge apparatus

Abstract

A piezoelectric body contains a ferroelectric substance phase having characteristics such that, in cases where an applied electric field is increased from the time free from electric field application, phase transition of the ferroelectric substance phase to a ferroelectric substance phase of a different crystal system occurs at least two times. The piezoelectric body should preferably be actuated under conditions such that a minimum applied electric field Emin and a maximum applied electric field Emax satisfy Formula (1): Emin<E1<Emax  (1) wherein the electric field E 1 represents the electric field at which the first phase transition of the ferroelectric substance phase begins.

1. A piezoelectric body, comprising a ferroelectric substance having characteristics such that, in cases where the ferroelectric substance is in a first ferroelectric substance phase and an applied electric field is increased from the time free from electric field application, the ferroelectric substance undergoes phase transition from the first ferroelectric substance phase to a second ferroelectric substance phase of a different crystal system and then to a third ferroelectric substance phase of a different crystal system. 
   
   
     2. A piezoelectric body as defined in  claim 1  wherein the piezoelectric body is actuated under conditions such that a minimum applied electric field Emin and a maximum applied electric field Emax satisfy Formula (1):
   Emin<E1<Emax  (1) 
 
     wherein the electric field E 1  represents the electric field at which the phase transition from the first to second ferroelectric substance phases begins. 
   
   
     3. A piezoelectric body as defined in  claim 2  wherein the piezoelectric body is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (2):
   Emin<E1<E2<Emax  (2) 
 
     wherein the electric field E 2  represents the electric field at which the phase transition from the second to third ferroelectric substance phases begins. 
   
   
     4. A piezoelectric body as defined in  claim 3  wherein the piezoelectric body is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (3):
   Emin<E1<E2≦E3<Emax  (3) 
 
     wherein the electric field E 3  represents the electric field at which the phase transition to the third ferroelectric substance phase finishes approximately perfectly. 
   
   
     5. A piezoelectric body as defined in  claim 1  wherein the piezoelectric body contains a body selected from the group consisting of an epitaxial film, a crystal orientational film, and a particulate orientational ceramics sintered body. 
   
   
     6. A piezoelectric body as defined in  claim 5  wherein the ferroelectric substance includes a phase having crystal orientational characteristics in a direction different from a direction of a spontaneous polarization axis. 
   
   
     7. A piezoelectric body as defined in  claim 6  wherein the ferroelectric substance is rendered at a phase having the crystal orientational characteristics in a direction approximately identical with the direction of the spontaneous polarization axis at a stage after a last phase transition has occurred in cases where the applied electric field is increased from the time free from electric field application. 
   
   
     8. A piezoelectric body as defined in  claim 1  wherein the first ferroelectric substance phase is a tetragonal phase having (100) orientation at the time free from electric field application and has the characteristics such that, in cases where the applied electric field is increased from the time free from electric field application, the ferroelectric substance undergoes successively the phase transition from the tetragonal phase to a rhombohedral phase, and the phase transition from the rhombohedral phase to a tetragonal phase having (001) orientation. 
   
   
     9. A piezoelectric body as defined in  claim 1  wherein the piezoelectric body contains at least one kind of perovskite type oxide and may contain inevitable impurities. 
   
   
     10. A piezoelectric body as defined in  claim 9  wherein the piezoelectric body contains at least one kind of perovskite type oxide and may contain inevitable impurities, the perovskite type oxide being represented by the general formula:
   general formula ABO 3    
 
     wherein A represents the element at the A site and represents at least one kind of element selected from the group consisting of Pb, Ba, La, Sr, Bi, Li, Na, Ca, Cd, Mg, K, and lanthanide elements,
 B represents the element at the B site and represents at least one kind of element selected from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, and Ni, and 
 O represents the oxygen atom, 
 the standard composition being such that each of the ratio of the total number of mols of the A site elements to the number of mols of the oxygen atom and the ratio of the total number of mols of the B site elements to the number of mols of the oxygen atom is 1:3, with the proviso that each of the ratio of the total number of mols of the A site elements to the number of mols of the oxygen atom and the ratio of the total number of mols of the B site elements to the number of mols of the oxygen atom may deviate from 1:3 within a range such that the perovskite structure is capable of being attained. 
 
   
   
     11. A piezoelectric body as defined in  claim 1  wherein each of the phase transition to the second ferroelectric substance phase due to electric field induction and the phase transition to the third ferroelectric substance phase due to electric field induction occurs at a temperature falling within the range of −50 ° C. to +200 ° C. 
   
   
     12. A piezoelectric device, comprising:
 i) a piezoelectric body as defined in  claim 1 , and 
 ii) electrodes for applying an electric field across the piezoelectric body. 
 
   
   
     13. A piezoelectric body as defined in  claim 1  wherein the piezoelectric body is capable of transitioning between a plurality of ferroelectric substance phases having different crystal systems in a state free from electric field application. 
   
   
     14. A piezoelectric body as defined in  claim 1 , wherein the piezoelectric body is capable of being in at least one of:
 a ferroelectric substance phase, in which phase transition does not occur in response to application of an increasing electric field, from a time when the piezoelectric body is free from electric field application, and 
 another ferroelectric substance phase, in which phase transition to a ferroelectric substance phase of a different crystal system occurs only once in response to application of an increasing electric field, from the time the piezoelectric body is free from electric field application. 
 
   
   
     15. A piezoelectric body as defined in  claim 13  that contains a tetragonal phase T(c) having the (001) orientation, a rhombohedral phase R having the (100) orientation, and a tetragonal phase T(a) having the (100) orientation in a state free from electric field application. 
   
   
     16. A piezoelectric body as defined in  claim 10  that contains Nb doped lead zirconate titanate. 
   
   
     17. A method for actuating a piezoelectric element equipped with a piezoelectric body and electrodes for applying an electric field to the piezoelectric body in a predetermined direction, the piezoelectric body comprising a ferroelectric substance having characteristics such that, in cases where the ferroelectric substance is in a first ferroelectric substance phase and an applied electric field is increased from the time free from electric field application, the ferroelectric substance undergoes phase transition from the first ferroelectric substance phase to a second ferroelectric substance phase of a different crystal system and then to a third ferroelectric substance phase of a different crystal system, comprising the steps of:
 applying the electric field; and 
 increasing the applied electric field; 
 the electric field being applied under conditions such that a minimum applied electric field Emin and a maximum applied electric field Emax satisfy Formula (1):
   Emin<E1<Emax  (1) 
 
 
     wherein the electric field E 1  represents the electric field at which the phase transition from the first to second ferroelectric substance phases begins. 
   
   
     18. A method for actuating a piezoelectric element as defined in  claim 17 , wherein the piezoelectric element is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (2):
   Emin<E1<E2<Emax  (2) 
 
     wherein the electric field E 2  represents the electric field at which the phase transition from the second to third ferroelectric substance phases begins. 
   
   
     19. A method for actuating a piezoelectric element as defined in  claim 18 , wherein the piezoelectric element is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (3):
   Emin<E1<E2 E3<Emax  (3) 
 
     wherein the electric field E 3  represents the electric field at which the phase transition to the ferroelectric substance phase finishes approximately completely. 
   
   
     20. A piezoelectric device, comprising:
 a piezoelectric element equipped with a piezoelectric body and electrodes for applying an electric field to the piezoelectric body in a predetermined direction; and 
 a controller which controls actuation of the piezoelectric element, 
 wherein
 the piezoelectric body comprises a ferroelectric substance having characteristics such that, in cases where the ferroelectric substance is in a first ferroelectric substance phase and an applied electric field is increased from the time free from electric field application, the ferroelectric substance undergoes phase transition from the first ferroelectric substance phase to a second ferroelectric substance phase of a different crystal system and then to a third ferroelectric phase of a different crystal system; and 
 
 the electric field being applied under conditions such that a minimum applied electric field Emin and a maximum applied electric field Emax satisfy Formula (1):
   Emin<E1<Emax  (1) 
 
 
     wherein the electric field E 1  represents the electric field at which the phase transition from the first to second ferroelectric substance phases begins. 
   
   
     21. A liquid discharge apparatus, comprising:
 i) a piezoelectric device as defined in  claim 20 , and 
 ii) a liquid storing and discharging member provided with:
 a) a liquid storing chamber, in which a liquid is to be stored, and 
 b) a liquid discharge opening, through which the liquid is to be discharged from the liquid storing chamber to the exterior of the liquid storing chamber. 
 
 
   
   
     22. A piezoelectric device as defined in  claim 20 , wherein the piezoelectric element is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (2):
   Emin<E1<E2<Emax  (2) 
 
     wherein the electric field E 2  represents the electric field at which the phase transition from the second to the third ferroelectric substance phases begins. 
   
   
     23. A piezoelectric device as defined in  claim 22 , wherein the piezoelectric element is actuated under conditions such that the minimum applied electric field Emin and the maximum applied electric field Emax satisfy Formula (3):
   Emin<E1<E2 E3<Emax  (3) 
 
     wherein the electric field E 3  represents the electric field at which the phase transition to the third ferroelectric substance phase finishes approximately completely.